1. Field of the Invention
The invention relates to a radiation-sensitive composition and a compound.
2. Discussion of the Background
When deep ultraviolet rays (e.g., KrF excimer laser light or ArF excimer laser light) or the like are applied to a chemically-amplified radiation-sensitive resin composition, an acid is generated in the exposed area, and a difference in solubility rate in a developer occurs between the exposed area and the unexposed area due to chemical reactions catalyzed by the generated acid. A resist pattern is formed on a substrate by utilizing the difference in solubility rate (see Japanese Patent Application Publication (KOKAI) No. 59-45439 and Perfluorooctyl Sulfonates; Proposed Significant New Use Rule).
A photoacid generator included in the chemically-amplified radiation-sensitive resin composition is required to exhibit excellent transparency to radiation and have a high quantum yield when generating an acid. An acid generated by the photoacid generator is required to have sufficient acidity, a sufficiently high boiling point, and an appropriate diffusion distance (hereinafter may be referred to as “diffusion length”) within the resist film, for example.
When using an ionic photoacid generator, the structure of the anion moiety is important in order to obtain sufficient acidity, a sufficiently high boiling point, and an appropriate diffusion length.
For example, a photoacid generator having a trifluoromethanesulfonyl structure generates an acid having sufficient acidity, and sufficiently increases the resolution of the photoresist. However, an acid generated by such a photoacid generator has a low boiling point and an inappropriate diffusion length. Specifically, sufficient resolution may not be obtained due to a long acid diffusion length.
A photoacid generator having a sulfonyl structure bonded to a large organic group (e.g., 10-camphorsulfonyl structure) generates an acid having a sufficiently high boiling point and an appropriate diffusion length (i.e., a sufficiently short diffusion length). However, the photoacid generator having a camphorsulfonyl structure may not be sufficiently dissolved in a solvent generally used for a radiation-sensitive resin composition due to poor solubility.
When precisely controlling the line width (e.g., when the device design dimensions are equal to or less than sub-half micrometers), it is important for a chemically-amplified resist to exhibit an excellent resolution and provide excellent surface flatness. When using a chemically-amplified resist that provides poor surface flatness, elevations and depressions (hereinafter may be referred to as “nano edge roughness”) formed on the surface of the resist film may be transferred to a substrate when transferring the resist pattern to the substrate by etching or the like, so that the dimensional accuracy of the pattern may deteriorate. This may impair the electrical properties of the resulting device (see J. Photopolym. Sci. Tech., p. 571 (1998), Proc. SPIE, Vol. 3333, p. 313, Proc. SPIE, Vol. 3333, p. 634, and J. Vac. Sci. Technol. B16 (1), p. 69 (1998), for example).